According to the prior art of a tool cart disclosed in U.S. Pat. No. 7,699,413, the tool cart is designed as a big box with wheels at its bottom corners. There is a plurality of drawers defined in the tool cart, and the tool cart has a top cover with an extra storage space for hand tools or parts to be placed. The advantages of the tool cart are its sufficient space allowing tools or parts to be stored or hanged and its convenience for being moved, but there are still certain disadvantages from the prior art:
1. The tool cart is unable to be detached and it takes up a lot of space. Therefore, its convenience of usage is limited.
2. The tool cart is unable to be detached and, therefore, its side tray or drawer can not be carried out by itself.
3. The tool cart is not detachable and its volume can not be reduced to improve its convenience of carrying.
4. The tool cart is not meshed with open structure for hanging other materials.
5. The side trays or drawers on the tool cart are not detachable for the tool cart to be functioned as a regular rack.
6. The storage space of the tool cart is not able to be expanded.